Maximum rebar cover from edge of concrete?
Hello, everyone. I’m new here. I have a question I’m hoping someone can answer. Is there a maximum clearance requirement for how far a piece of rebar should be from the edge of concrete?
For reference, I have a manufacturer that built some precast stair treads that are 42in wide x 12in deep x 2.5in thick. The end customer had a couple stair treads break while handling (mishandling) them, and he noticed on one end, the rebar was about 2” away from the edge and, on the other end, it was about 5” away from the edge. The question is now is the 5” an acceptable gap? These treads are mounted on stringers with each end sitting on a piece of angle iron that the tread attaches to via a threaded insert that is cast into the concrete and bolted in to through the angle iron.
Any help is appreciated, especially if you can point me to where a spec is called out by ASTM or something similar.
Thank you.
Replies
There are no specific ASTM spec for rebar location, it mentioned in ASTM it likely refers you to ACI. There are 3 conditions governing rebar location. 1) Concrete cover. If this is an interior stair then there must 3/4" of concrete cover (i.e. distance from surface of bar to surface of concrete). 2) Structural reinforcement. These bars give the stair slab strength from support to support. These are probably the bars you're referring to. Their spacing is governed by the structural design, as well as concrete cover requirements. 3) Temperature/shrinkage reinforcing. For a stair this is commonly just the nosing bars (one bar parallel to the intersection of the riser with the tread on the top). Concrete cover is typically what applies here. While there is a minimum (3/4" to 2") it will depend on the exposure conditions.
A photo of what you have would help.